1. Field of the Invention
The present invention relates to a detection apparatus that detects a feature point of an image, a detection method, and a storage medium.
2. Description of the Related Art
In the field of computer vision, there is a process called feature point detection (or feature point extraction). Feature point detection refers to a process for detecting points on an image that is obtained by imaging an object at which points the object can be conspicuously detected as feature points. According to Yasushi Kanazawa and Kenichi Kanatani, “Detection of Feature Points for Computer Vision”, The Journal of Institute of Electronics, Information, and Communication Engineers, Vol. 87, No. 12, pp. 1043-1048, 2004, there are a wide variety of feature point detection methods including the Harris operator.
Feature point detection has, for example, the following applications. Feature points are detected from successive images, and feature amounts of these feature points are calculated. Furthermore, if the feature amount of a feature point in an image has the highest similarities to the feature amount of a feature point in another image, and those feature points are associated with each other, the relative position between those feature points can be regarded as the moving amount of a feature point. From this moving amount, a movement of an object or the entire image in which this feature point is contained can be obtained. For example, if a movement caused by camera shake is contained in an image, camera shake correction processing can be performed by performing geometric conversion in such a manner that the moving amount is corrected.
Also, if feature points are detected from a stereo image that is composed of two right and left images, the depth of a feature point can be estimated using the principle of triangulation based on the relative position between feature points detected from the respective images and associated with each other. That is to say, a three-dimensional image can be created from a stereo image.
Feature point detection has various other applications including image retrieval, image recognition, etc.
When feature points are to be detected from an image, such as an image with a shallow depth of focus and a wide out-of-focus area, from which it is difficult to detect feature points, there are cases where a set target number of feature points cannot be detected. Thus, conventional configurations in which feature point detection is performed had the problem of a decrease in the performance of processing, such as shake correction processing, that is executed using the results of the obtained feature points.
The present invention provides a technology for detecting a sufficient number of feature points accurately with a small processing load.